Those arguing for action say such discrimination is outlawed in India and they want similar protection in Britain too.

One of the protestors, Ravi Kumar of Anti Caste Discrimination Alliance, said: "We are here today because we are demanding equality, respect and dignity in the United Kingdom.

"Caste discrimination has been going on for decades (in Britain). What we have found is that it has actually increased over the last decade or so because of social media and people have gone back to their previous caste identities."

In the House of Commons the government acknowledged the existence of caste discrimination in Britain. But it said it does not think legislation will help to stamp it out.

'Sub-human'

Equalities minister Jo Swinson told MPs: "This is an issue that is contained in the Hindu and Sikh communities.

"That's why we are working with those communities to address these problems."

This is a straightforward issue, caste discrimination in the work place is wrong and the people who suffer from it deserve legal protection.Richard Fuller, Conservative MP

She warned of concern that legislation could increase stigma rather than ease the problem. That's why the government was planning to tackle caste prejudice through an education programme instead.

There are thought to be around 400,000 low caste people in Britain.

Campaigner Davinder Prasad of Castewatch UK said many of them had experienced some form of discrimination.

He called it an invisible disease" that non-Asians were only starting to become aware of in Britain.

"The caste system is absolutely horrible for the victims. It makes you feel sub-human. There is no description for the pain that victims feel," he said.

During the debate many MPs backed the protestors.

Conservative MP Richard Fuller said: "This is a straightforward issue, caste discrimination in the work place is wrong and the people who suffer from it deserve legal protection. That's it. Beginning and end."

Lords vote

Shadow business secretary Chuka Umunna said that caste discrimination was "completely unacceptable".

"Every community group, every faith group we have spoken to, on each side of this debate in recent days has been united in the belief that caste discrimination has no place in our country," he said.

Last month, the House of Lords voted by a majority of 103 to amend the Equality Act to include caste discrimination.

That raised the hopes of campaigners. Meena Varma said protestors had come from all over the country to back the call for a ban on caste discrimination.

"I think there is in excess of a thousand people here today," she said.

"We've had coaches from Wolverhampton, Birmingham, Coventry, Southall and Bedford. People from across the country have come here to demand justice today."

The government has asked the Equality and Human Rights Commission to examine the nature of caste prejudice and harassment, and consider what other action might be helpful.